• Fracture toughness and fracture energy of rock-concrete interfaces decrease with increasing temperature across different lithologies, with sandstone-concrete interface most affected.
• At elevated temperatures, fracture parameters become less sensitive to interface strength factor, indicating thermal effects dominate failure.
• Fracture process zone length increases linearly with temperature, signifying a brittle-to-ductile transition.
• Findings provide critical insights for designing and ensuring safety of deep underground structures under thermo-mechanical coupling.